Model material for dental applications

ABSTRACT

A modeling material for dental purposes comprises at least one metal and/or at least one metal compound which are able to react chemically with one another and/or with at least one further reactant so as to lead to an increase in volume, and at least one substance having thermoplastic and/or wax-like properties. If desired, a glass-ceramic, a glass and/or an oxide-ceramic material and, if desired, an additive, in particular a dispersant, can additionally be present. The modeling material is particularly suitable for compensating for the sintering shrinkage which occurs in the production of ceramic shaped dental parts.

The invention relates to a modeling material for dental purposes, aprocess for preparing it and its use.

Ceramic or “porcelain” was always an attractive material for producingartificial teeth having a very tooth-like appearance in terms of shapeand color. Ceramic is a chemically resistant, corrosion-resistant andbiocompatible material which, in addition, is available in virtuallyunlimited amounts in mineral form and is thus inexpensive. Individualtooth replacement can be produced simply and reproducibly from thismaterial by means of the techniques of a dental technician, so that“dental ceramics” have become established as a material.

To overcome the only weakness of this material, viz. the brittleness,tooth replacement manufactured by dental techniques has generally beenproduced for a long time as a classical composite material, i.e. ascermet. A cermet crown or bridge comprises a metal framework orsubstructure and a facing of dental ceramic which reproduces the shapeof the tooth. To install the tooth replacement, the substructure isfastened directly on the remaining part of the tooth after preparationby the dentist and is often referred to as (protective) cap. Dependingon the material or alloy of which the caps consist and, depending on theproduction method (casting, electroforming, i.e. electrodeposition),problems in the form of corrosion and resulting discoloration,incompatibility with the body, etc, can arise. There has therefore beenincreasing development in recent years of systems which can producecomparable substructures of ceramic material and process them further bythe techniques of a dental technician.

There are already a number of functioning systems on the dental market.Thus, the ceramic caps are, for example, produced by manual applicationof a slip to a model stump, subsequent sintering and infiltration withspecial glass (VITA In-Ceram) or by means of a hot pressing process(Empress, IVOCLAR). There are also systems in which the caps aredigitally milled from sintered or presintered ceramic blocks(DCS-System, CEREC, etc). However, it is generally the case that none ofthe all-ceramic systems mentioned achieve the accuracy of fit ofmetallic bodies on the remainder of the tooth, regardless of whether themetallic bodies have been cast or formed by electrodeposition processes.In addition, these systems are usually very expensive to purchase.

The lack of accurate fit of existing all-ceramic systems is mainly dueto the shaping methods used. Metallic caps are produced by casting orelectrodeposition, so that the metal in molten or dissolved form canoptimally match the stump geometry. On the other hand, in the case of,for example, CADCAM all-ceramic methods, a solid material has to bemilled with removal of material according to a digitally recorded dataset. However, scanning of the tooth stump and the milling can, dependingon the digital resolution of the system components, itself containinaccuracies.

A further fundamental difficulty with all existing or future systems forproducing all-ceramic tooth replacement from sintered ceramic materialswith regard to the accuracy of fit of the finished parts is ceramicshrinkage, i.e. the volume shrinkage of shaped ceramic parts associatedwith the densifying sintering process. Although this sintering shrinkagecan be reduced to a certain extent, it cannot be avoided completely. Forthis reason, the sintering shrinkage associated with the sintering stepis, for example, avoided indirectly by processing previously sinteredceramic (CADCAM method, see above) or seeking to achieve a pore-freesolid microstructure in another way (glass infiltration of the soft,porous ceramic cap in the InCeram method, see above). In the case ofelectrophoretic deposition of ceramic particles, too, the shaped ceramicpart obtained subsequently has to be sintered, so that the indicatedproblem of sintering shrinkage also arises here.

DE-C1-197 03 032 and DE-A1-100 44 605 describe compositions of hotcasting compounds and their use for producing corresponding sinteredbodies. However, what is described in the first of these texts is theproduction of sheet-like ceramic or powder-metallurgical componentswhich are structured on one side, for example cooling elements orsubstrates for electronic components. Although DE-A-100 44 605 doesmention that tooth replacement can be produced using the moldingcompositions claimed, it is not concerned with the abovementionedproduction of ceramic tooth replacement using dental models (stumpmodels).

DE-A1-4324438 describes a process for producing oxide-ceramic toothreplacement pieces in which the sintering shrinkage is preventeddirectly during sintering by addition of particles of readily oxidizablemetals, metal suboxides or metal hydrides. However, since this processdoes not use dental models (stump models), it cannot be applied to theabove-described applications. An analogous situation applies in the caseof DE-C1-195 47 129. There too, the sintering shrinkage of the sinteredceramic body is supposed to be prevented directly during sintering.

It is therefore an object of the invention to help make it possible toachieve a high accuracy of fit of all-ceramic shaped dental parts withthe base structures for which they are intended. In particular, thedisadvantageous effects of the sintering shrinkage indicated should beavoided.

This object is achieved by the modeling material having the features ofclaim 1, by the processes of claim 26 and claim 28 and by the useclaimed in claim 27. Preferred embodiments are described in thedependent claims 2 to 25 and 29 and 30, respectively. The wording of allclaims is hereby incorporated by reference into the present description.

The modeling material of the invention for dental purposes comprises atleast one metal and/or at least one metal compound and at least onesubstance having thermoplastic and/or wax-like properties. The metaland/or the metal compound are, according to the invention, able to reactchemically with one another and/or with at least one further reactant soas to lead to an increase in volume. Preference is given to the metaland/or the metal compound forming a first component within the materialand the thermoplastic/wax-like substance forming a second component.

The modeling material described has the advantage that it is expandable(due to the ability of the chemical reaction to be carried out). Thisexpandability can be adjusted within wide limits, as explained in moredetail below. The sintering shrinkage occurring during the actualproduction of the shaped ceramic dental part can in this way be takeninto account as early as the production of the dental model (for exampleworking model). For this purpose, the expandability of the modelingmaterial is defined and set according to the (known) sintering shrinkageof the ceramic material used for producing the tooth replacement. Inthis way, shaped dental parts which precisely fit the preparation in themouth (e.g. tooth stump) or prosthetic buildup parts can be produced.

The composition of the material of the invention can in principle bechosen at will as long as an appropriate increase in volume is possibleas a result of some chemical reaction. However, the composition ispreferably chosen so that it is possible to carry out a chemicalreaction in which an increase in the oxidation number of the metal or ofthe metal of the metal compound occurs. Such an increase in theoxidation number is, as is known, a possible definition of the term“oxidation”. It therefore includes not only a reaction with oxygen, i.e.an oxidation in the relatively narrow sense, but also, for example, anitridation.

In further preferred embodiments of the modeling material of theinvention, its composition is chosen so that a chemical reaction with anoxygen-containing compound as other reactant or preferably with oxygenas other reactant is possible. Such a chemical reaction can thereforeoccur in the simplest way by reaction with atmospheric oxygen. Thechemical reaction then corresponds precisely to the abovementioned“classical” definition of oxidation.

The metal or the metal of the metal compound can, according to theinvention, advantageously be a transition metal. Within this group,particular mention may be made of the transition metals of the fourthtransition group, with titanium being particularly preferred.

In further preferred embodiments of the modeling material of theinvention, the metal compound is the compound of a metal with (at leastone) nonmetal. In such cases, the modeling material therefore does notcontain any intermetallic compounds, i.e. no chemical compounds made upof two or more metallic elements. The modeling material in such casespreferably comprises nitrides, carbides or borides as metal compounds,with preference being given to using nitrides. The compounds mentionedare preferred because, inter alia, they can frequently readily bereacted chemically with oxygen/atmospheric oxygen to produce a volumeexpansion.

According to the invention, all substances having thermoplastic and/orwax-like properties can in principle be used. The definition of suchsubstances is known to those skilled in the art; additional referencemay be made, for example, to the definitions in Römpp-Lexikon, GeorgThieme Verlag. For the purposes of the invention, these substances serveto provide processibility and moldability of the metals/metal compoundswhich are generally in powder form. The substances concerned arepreferably waxes, with the modeling material of the invention comprisingin particular at least one paraffin wax. Depending on the composition,the modeling material of the invention can become solid at verydifferent temperatures. Owing to the indicated use of these modelingmaterials, it is, however, preferred that the material has asolidification point in the range from 50° C. to 80° C., in particularfrom 55° C. to 70° C. Advantages resulting therefrom will be addressedlater in connection with the preferred storage form of the modelingmaterial.

Furthermore, the consistency and in this context the viscosity of themodeling material can be set with a view to its use. Since it is usualto fill negative molds of a tooth preparation or a prosthetic builduppart with the modeling material, the modeling material should have aflow limit and have a comparatively low viscosity above thesolidification point. Above the solidification point and above the flowlimit, it can flow readily and quickly into the appropriate molds. Aftercooling to temperatures significantly below the solidification point,the modeling material is solid enough to be demolded (i.e. removed fromthe model) without becoming deformed. On renewed heating of the demoldedmodeling material to above the solidification point but withoutovercoming the flow limit, its shape is retained. However, the flowlimit is ideally not too high, so that the user of the material, i.e.generally a dental technician, can overcome it by means of simplemeasures such as stirring with a spatula or use of a vibrator.

In the case of further, preferred embodiments, the modeling material ofthe invention further comprises at least one glass-ceramic, a glass oran oxide-ceramic material. Glasses are, as is known, quite generallysubstances in the amorphous, noncrystalline solid state, which can bedescribed physically as a frozen, supercooled melt. Glass-ceramics arepolycrystalline solids which are produced by controlled crystallization(devitrification) of glasses. The microstructure of glass-ceramicsdisplay both crystalline phases and glass-like, amorphous phases.Oxide-ceramic materials are ceramic materials which comprise (highlyrefractory) oxides and can also be made up of a plurality of oxides.They have a microstructure which is free of glass phases. According tothe invention, the materials mentioned are, in particular, used asconstituent of the first component defined at the outset. They aregenerally inert in respect of the chemical reaction serving to producethe increase in volume, i.e. they reduce the expandability of themodeling material if they are added to it. The materials mentioned arepreferably a glass-ceramic derived from silicate glass, silicate glassor an aluminum oxide ceramic. These materials are available in largequantities at a low price.

In further, preferred embodiments of the invention, the modelingmaterial further comprises at least one additive, in particular one ormore dispersants. These promote the mixing of the metal/metal compoundwith the thermoplastic/wax-like substance.

Such additives and dispersants are known in principle to those skilledin the art. Preference is here given to polyethylene glycols, inparticular polyethylene glycol ethers. The products marketed under thetrade name Brij by Fluka, Germany, may be mentioned by way of example.

As mentioned at the outset, the composition of the modeling materialcan, according to the invention, be adjusted within wide limits.However, compositions which achieve particular success according to theinvention will be defined below.

Thus, particular mention may be made of embodiments in which theproportion of the first component (metal/metal compound and, if desired,glass-ceramic, glass and/or oxide ceramic) is from 30% by volume to 80%by volume, based on the total volume of the material. Within this range,proportions of from 50% by volume to 75% by volume are particularlypreferred.

Preference is likewise given to embodiments in which the first componentpresent in the modeling material comprises, based on the total volume ofthis first component, from 1% by volume to 100% by volume of titaniumnitride and from 0% by volume to 99% by volume of glass-ceramic, glassand/or oxide ceramic. Within these ranges, preference is given toembodiments in which the first component either comprises from 3% byvolume to 25% by volume of titanium nitride and accordingly from 75% byvolume to 97% by volume of aluminum oxide or comprises from 40% byvolume to 99% by volume of titanium nitride and accordingly from 1% byvolume to 60% by volume of glass-ceramic or glass.

Mention should also be made of preferred particle sizes of the metalcompound and the added materials. Thus, the preferred particle size d₅₀of the metal compound, in particular the titanium nitride, is from 0.5μm to 8 μm. Within this range, particularly preferred particle sizes d₅₀are in the range from 0.5 to 1.5 μm or from 2 to 8 μm. The preferredparticle size d₅₀ of the oxide-ceramic material, in particular thealuminum oxide, is from 3 to 5 μm, in particular from 3.5 to 4 μm. Thepreferred particle size d₅₀ of the glass or the glass ceramic is lessthan 80 μm, in particular less than 30 μm.

If a first group of further preferred embodiments is to be specified,then particular mention should be made of modeling materials in whichthe first component comprises, based on the total volume of this firstcomponent, either from 1% by volume to 12% by volume of titaniumnitride, in particular from 3% by volume to 12% by volume of titaniumnitride, having a particle size d₅₀ of from 2 to 8 μm and from 88% byvolume to 99% by volume of aluminum oxide, preferably from 88% by volumeto 97% by volume of aluminum oxide, having a particle size d₅₀ of from 3to 5 μm or from 40% by volume to 60% by volume of titanium nitridehaving a particle size d₅₀ of from 2 to 8 μm and from 40% by volume to60% by volume of glass or glass-ceramic having a particle size d₅₀ ofless than 30 μm.

If a second group of further preferred embodiments is to be specified,then particular mention should be made of modeling materials in whichthe first component comprises, based on the total volume of this firstcomponent, either from 10% by volume to 25% by volume of titaniumnitride having a particle size d₅₀ of from 0.5 to 1.5 μm and from 75% byvolume to 90% by volume of aluminum oxide having a particle size d₅₀ offrom 3 to 5 μm or from 70% by volume to 95% by volume of titaniumnitride having a particle size d₅₀ of from 0.5 to 1.5 μm and from 5% byvolume to 30% by volume of glass or glass-ceramic having a particle sized₅₀ of less than 30 μm.

With regard to the composition of the modeling material of the inventionin respect of the additive which is added, the amounts of this are basedon the (total) particle surface area of metal/metal compound and, ifused, of glass-ceramic, glass and/or oxide ceramic. Amounts of additiveof from about 0.5 to 10 mg, preferably from 1 to 4 mg, per m² ofparticle surface area may be mentioned here.

As indicated above, the expandability of the modeling material of theinvention can be varied within wide limits by choice of the composition.Normally, a linear expandability of the material of from 3 to 50%, inparticular from 5 to 30%, will be set to compensate for a sinteringshrinkage which usually occurs. Within this range, preference is givento a linear expandability of from 10% to 25% to compensate for usualsintering shrinkages of dental ceramics. As mentioned above, theexpansion occurring due to the reaction of the metal/metal compound canbe reduced and thus set by addition of the materials mentioned. Thelatter are inert in the reaction and do not expand. Thus, for example,the (calculated) linear expansion of titanium nitride (TiN) in theoxidation to titanium dioxide (TiO₂) is 18.1%, which can be reduced byaddition of glass-ceramic, glass and/or oxide-ceramic materials.

In this context, a further effect occurring in the case of the modelingmaterial of the invention can be utilized. Thus, titanium nitrideexpands in the reaction to form titanium dioxide not only by the valueindicated above but also to a much greater degree. This can beattributed to the fact that there is an increase in the porosity inaddition to the chemical reaction indicated above. This “superexpansion”enables a modeling material according to the invention having anexpandability of, for example, 30% or even above to be provided. Areduction in the expansion can be achieved by mixing in preferablyrelatively large amounts of the abovementioned (inert) materials. Thismakes it possible to set, for example, the preferred values for thelinear expandability of from 10 to 25%. The opportunity of reducing thevolume expansion by mixing in relatively large amounts of glass-ceramic,glass and/or oxide-ceramic material has the advantage that dental modelshaving high strengths can be obtained. In addition, the microstructureof the dental model can be adjusted. The remaining (open) porosity ofthe dental model produced using the modeling material of the inventionalso has the advantage that it can be utilized for introduction ofgasses or liquids or for their removal (e.g. during drying).

The modeling material can be stored for a very long time, in particularbelow its solidification point, i.e. in the solidified state, since nodemixing of the components can take place. The modeling material ispreferably provided in the form of granules, in particular in the formof largely droplet-shaped granules. In this way, the material can,particularly when used for its intended purpose, be metered in a simplefashion, for example by weighing. To make it possible to achieve thecorresponding customary weighing accuracies here, the diameter of theabovementioned granules is preferably in the range from 2 to 20 mm, inparticular from 5 to 15 mm. A final point which should be made in thiscontext is that the modeling material of the invention can be present ina packaging means which can be closed, preferably closed in an airtightfashion, or a corresponding container.

The invention further provides a process for preparing the modelingmaterial of the invention. Here, a first component comprising at leastone metal and/or at least one metal compound which can react chemicallywith one another and/or with at least one further reactant so as to leadto an increase in volume, if desired after addition of at least oneglass-ceramic, a glass and/or an oxide-ceramic material, is dispersedwith a second component comprising at least one substance havingthermoplastic and/or wax-like properties, if desired after addition ofat least one additive. The procedure described has the advantage thatvery good interaction of the constituents of the material is achieved byuse of the two components. In this context, attention may be drawn tothe examples below in which this procedure is described in more detail.

In addition, the invention encompasses the use of the modeling materialof the invention for producing shaped dental parts, in particularall-ceramic shaped dental parts, i.e. ones in which the shaped part ismade up entirely of ceramic material. In this use according to theinvention, the sintering shrinkage occurring on sintering of a greenceramic body formed on a working model is at least partly compensated bythe expansion of the modeling material (in the production of the workingmodel). The sintering shrinkage is preferably fully compensated, so thatthe shaped dental part obtained after sintering has dimensions whichcorrespond exactly to the preparation in the mouth or a prostheticbuildup part.

Finally, the invention provides a process for producing a dental model.In this process, the modeling material of the invention is introducedinto a negative mold of a tooth preparation or of a prosthetic builduppart and a chemical reaction which proceeds with an increase in volumeof the material is initiated and carried out.

In accordance with what has been said above about the modeling materialitself, the process of the invention is further characterized in thatthe chemical reaction is an oxidation, preferably an oxidation by meansof oxygen (or in particular atmospheric oxygen) as further reactant.

In all specified embodiments of the process of the invention, thechemical reaction is preferably initiated and carried out by means of athermal treatment. Basically, it is possible to employ temperatureswithin a broad temperature range, with a thermal treatment attemperatures in the range from 200° C. to 1250° C. being preferred. Thisapplies, by way of example and in particular, to cases in which anoxidation of the modeling material in air, i.e. by means of atmosphericoxygen, is carried out.

The features described and further features of the invention can bederived from the description of the examples below in conjunction withthe subordinate claims. The individual features can be realized alone orin combination with one another.

EXAMPLE 1

104.24 g of aluminum oxide (particle size d₅₀=3.8 μm) and 15.76 g oftitanium nitride (particle size d₅₀=6.4 μm) are milled together in aplanetary mill for about 4 hours (component 1). This corresponds to avolume ratio of 90% of aluminum oxide to 10% of titanium nitride.Ethanol is used as dispersion medium for milling and aluminum oxidemilling pots and balls are employed. The mixture is subsequently driedat 80-100° C. 16.63 g of paraffin (solidification point: 62-64° C.) and0.79 g of Brij 72® are melted in a vessel heated to 85° C. (component2). While stirring, the likewise heated powder mixture (component 1) isslowly added thereto. A high-speed stirrer disk having a diameter of 50mm is used for stirring and the mixture is dispersed at about 2000 rμmfor 1 hour. This gives a homogeneous, paste-like composition which canbe used for molding immediately. The composition can be stored in thesolidified state, for which purpose it is divided into droplet-shapedgranules having a diameter of 5-15 mm. Before further use, the desiredamount has to be metered, heated to 80° C. and redispersed by stirring.

The molds comprise a silicone rubber which have been heated to about 80°C. before being filled with the composition described here. To fill themolds, they are placed on a vibrator and the flowable composition isintroduced into the mold, with inclusion of air being avoided. Vibrationaids filling of the mold and outgassing of the composition. Aftercooling, the shaped body consisting of the composition according to theinvention is demolded.

This shaped part is embedded in a bed of aluminum oxide powder anddewaxed and oxidized in a suitable oven. The following temperatureprofile is used for this purpose:

Heat at 0.5 K/min from room temperature to 200° C. and hold for 2 hours,heat at 0.5 K/min to 250° C. and hold for 1 hour, heat at 2 K/min to1200° C. and hold for 2 hours, allow to cool. The linear expansionachieved is 18%.

EXAMPLE 2

89.54 g of aluminum oxide (particle size d₅₀=3.8 μm) and 30.46 g oftitanium nitride (particle size d₅₀=1.2 μm) are milled together in aplanetary mill for about 4 hours (component 1). This corresponds to avolume ratio of 80% of aluminum oxide to 20% of titanium nitride.Ethanol is used as dispersion medium for milling and aluminum oxidemilling pots and balls are employed. The mixture is subsequently driedat 80-100° C. 16.09 g of paraffin (solidification point: 62-64° C.) and0.74 g of Brij 72® are melted in a vessel heated to 85° C. (component2). While stirring, the likewise heated powder mixture (component 1) isslowly added thereto. A high-speed stirrer disk having a diameter of 50mm is used for stirring and the mixture is dispersed at about 2000 rμmfor 1 hour. This gives a homogeneous, paste-like composition which canbe used for molding immediately. The composition can be stored in thesolidified state, for which purpose it is divided into droplet-shapedgranules having a diameter of 5-15 mm. Before further use, the desiredamount has to be metered, heated to 80° C. and redispersed by stirring.

The molds comprise a silicone rubber which have been heated to about 80°C. before being filled with the composition described here. To fill themolds, they are placed on a vibrator and the flowable composition isintroduced into the mold, with inclusion of air being avoided. Vibrationaids filling of the mold and outgassing of the composition. Aftercooling, the shaped body consisting of the composition according to theinvention is demolded.

This shaped part is embedded in a bed of aluminum oxide powder anddewaxed and oxidized in a suitable oven. The following temperatureprofile is used for this purpose:

Heat at 0.5 K/min from room temperature to 200° C. and hold for 2 hours,heat at 0.5 K/min to 250° C. and hold for 1 hour, heat at 2 K/min to1200° C. and hold for 2 hours, allow to cool. The linear expansionachieved is 11.5%.

EXAMPLE 3

134.52 g of glass-ceramic powder (composition in % by mass: 57.8 SiO₂,13.8 Al₂O₃, 10.4 Na₂O, 8.7 K₂O, 4.3 CaO, 1.9 SnO₂, 1.7 ZnO₂, 0.6 B₂O₃,0.2 ZrO₂; glass transformation point: 550° C., softening point: 620° C.,CTE: 12.7×10⁻⁶; proportion of leucite: 20-30%; particle size: d₉₀<10 μm)and 15.48 g of titanium nitride (particle size: d₅₀=1.2 μm) are added toabout 100 ml of ethanol and the suspension is dispersed by means of anultrasonic disintegrator. All of the ethanol is subsequently taken off.This powder mixture (component 1) has a volume ratio of 80% by volume ofglass-ceramic to 20% by volume of titanium nitride. 15.08 g of paraffin(solidification point: 62-64° C., and 2 g of Brij 72® are melted in avessel heated to 85° C. (component 2). While stirring, the likewiseheated powder mixture (component 1) is slowly added thereto. A propellerstirrer having a diameter of 50 mm is used for stirring and the powdermixture is stirred in at about 500 rμm and the mixture is subsequentlydispersed at about 1000 rμm for 1 hour. This gives a homogeneous,paste-like composition which is degassed by application of a vacuum (<10mbar) and can be used for molding immediately. The composition can bestored in the solidified state, for which purpose it is divided intodroplet-shaped granules having a diameter of 5-15 mm. Before furtheruse, the desired amount has to be metered, heated to 85° C. andredispersed by stirring.

The molds comprise a silicone rubber which have been heated to about 85°C. before being filled with the composition described here. To fill themolds, they are placed on a vibrator and the flowable composition isintroduced into the molds. The filled molds are then evacuated.Vibration and evacuation aids filling of the mold and outgassing of thecomposition. After cooling, the shaped body consisting of thecomposition according to the invention is demolded.

These shaped parts are embedded in a bed of aluminum oxide powder anddewaxed and oxidized in a suitable oven. The following temperatureprofile is used for this purpose:

Heat at 1 K/min from room temperature to 100° C., continue at 2 K/min to400° C., at 0.5 K/min to 420° C., at 0.4 K/min to 550° C. and at 4 K/minto a final temperature of 750° C. which is held for 30 minutes. Thelinear expansion achieved is 16.6%.

1. A modeling material for dental purposes, characterized in that itcomprises, preferably as a first component, at least one metal and/or atleast one metal compound which are able to react chemically with oneanother and/or with at least one further reactant so as to lead to anincrease in volume and, preferably as second component, at least onesubstance having thermoplastic and/or wax-like properties.
 2. Themodeling material as claimed in claim 1, characterized in that anincrease in the oxidation number of the metal or of the metal of themetal compound occurs in the chemical reaction.
 3. The modeling materialas claimed in claim 1, characterized in that the further reactant is anoxygen-containing compound or preferably oxygen.
 4. The modelingmaterial as claimed in claim 1, characterized in that the metal or themetal of the metal compound is a transition metal.
 5. The modelingmaterial as claimed in claim 4, characterized in that the metal or themetal of the metal compound is a transition metal of the fourthtransition group, in particular titanium.
 6. The modeling material asclaimed in claim 1, characterized in that the metal compound is acompound of a metal with a nonmetal, preferably a nitride, a carbide ora boride, in particular a nitride.
 7. The modeling material as claimedin claim 1, characterized in that the substance is a wax, preferably atleast one paraffin wax.
 8. The modeling material as claimed in claim 1,characterized in that it has a solidification point in the range from50° to 80° C., preferably from 55° to 70° C.
 9. The modeling material asclaimed in claim 1, characterized in that it further comprises,preferably as constituent of the first component, at least one glassand/or a glass-ceramic.
 10. The modeling material as claimed in claim 9,characterized in that the glass is a silicate glass or the glass-ceramicis derived from silicate glass.
 11. The modeling material as claimed inclaim 1, characterized in that it further comprises, preferably asconstituent of the first component, at least one oxide-ceramic material.12. The modeling material as claimed in claim 11, characterized in thatthe oxide-ceramic material is aluminum oxide.
 13. The modeling materialas claimed in claim 1, characterized in that it further comprises atleast one additive, in particular at least one dispersant.
 14. Themodeling material as claimed in claim 13, characterized in that theadditive is at least one polyethylene glycol, preferably at least onepolyethylene glycol ether.
 15. The modeling material as claimed in claim1, characterized in that the proportion of the first component is, basedon the total volume of the material, from 30% by volume to 80% byvolume, preferably from 50% by volume to 75% by volume.
 16. The modelingmaterial as claimed in claim 1, characterized in that the firstcomponent present in the modeling material comprises, based on the totalvolume of this first component, either from 1% by volume to 100% byvolume of titanium nitride, preferably from 3% by volume to 25% byvolume of titanium nitride, and from 0% by volume to 99% by volume ofoxide-ceramic material, in particular aluminum oxide, preferably from75% by volume to 97% by volume of oxide-ceramic material, in particularaluminum oxide, or from 1% by volume to 100% by volume of titaniumnitride, preferably from 40% by volume to 99% by volume of titaniumnitride, and from 0% by volume to 99% by volume of glass orglass-ceramic, preferably from 1% by volume to 60% by volume of glass orglass-ceramic.
 17. The modeling material as claimed in claim 16,characterized in that the particle size d₅₀ of the metal compound, inparticular the titanium nitride, is from 0.5 μm to 8 μm, preferably from0.5 to 1.5 μm or from 2 to 8 μm.
 18. The modeling material as claimed inclaim 16, characterized in that the particle size d₅₀ of theoxide-ceramic material, in particular the aluminum oxide, is from 3 to 5μm, preferably from 3.5 to 4 μm, or the particle size of d₅₀ of theglass or the glass-ceramic is less than 80 μm, preferably less than 30μm.
 19. The modeling material as claimed in claim 1, characterized inthat the first component present in the modeling material comprises,based on the total volume of this first component, either from 1% byvolume to 12% by volume of titanium nitride, in particular from 3% byvolume to 12% by volume of titanium nitride, having a particle size d₅₀of from 2 to 8 μm and from 88% by volume to 99% by volume of aluminumoxide, preferably from 88% by volume to 97% by volume of aluminum oxide,having a particle size d₅₀ of from 3 to 5 μm or from 40% by volume to60% by volume of titanium nitride having a particle size d₅₀ of from 2to 8 μm and from 40% by volume to 60% by volume of glass orglass-ceramic having a particle size of d₅₀ of less than 80 μm,preferably less than 30 μm.
 20. The modeling material as claimed inclaim 1, characterized in that the first component present in themodeling material comprises, based on the total volume of this firstcomponent, either from 10% by volume to 25% by volume of titaniumnitride having a particle size d₅₀ of from 0.5 to 1.5 μm and from 75% byvolume to 90% by volume of aluminum oxide having a particle size of d₅₀of from 3 to 5 μm or from 70% by volume to 95% by volume of titaniumnitride having a particle size d₅₀ of from 0.5 to 1.5 μm and from 5% byvolume to 30% by volume of glass or glass-ceramic having a particle sized₅₀ of less than 80 μm, preferably less than 30 μm.
 21. The modelingmaterial as claimed in claim 13, characterized in that the additive ispresent in an amount based on the particle surface area of metal and/ormetal compound and, if present, glass, glass-ceramic and/oroxide-ceramic material of from about 0.5 to 10 mg, preferably from 1 to4 mg, per m² of particle surface area.
 22. The modeling material asclaimed in claim 1, characterized in that the linear expandability ofthe material is in the range from 3 to 50%, preferably from 5 to 30%, inparticular from 10 to 25%.
 23. The modeling material as claimed in claim1, characterized in that it is in the form of granules, preferably inthe form of largely droplet-shaped granules.
 24. The modeling materialas claimed in claim 23, characterized in that the diameter of thegranules is in the range from 2 to 20 mm, preferably from 5 to 15 mm.25. The modeling material as claimed in claim 1, characterized in thatit can be stored in the solidified state, in particular in packagingwhich can be closed in an airtight fashion.
 26. A process for preparingthe modeling material as claimed in claim 1, characterized in that afirst component comprising at least one metal and/or at least one metalcompound which can react chemically with one another and/or with atleast one further reactant so as to lead an increase in volume, ifdesired after addition of at least one glass-ceramic, a glass and/or anoxide-ceramic material, is dispersed with a second component comprisingat least one wax, if desired after addition of at least one additive.27. The use of the modeling material as claimed in claim 1 for producingpreferably all-ceramic shaped dental parts, wherein the sinteringshrinkage occurring on sintering of a green ceramic body formed on aworking model is at least partly, preferably completely, compensated bythe expansion of the modeling material in the production of the workingmodel.
 28. A process for producing a dental model, in particular aworking model, characterized in that the modeling material as claimed inclaim 1 is introduced into a negative mold of a tooth preparation or ofa prosthetic buildup part and a chemical reaction which proceeds with anincrease in volume of the material in initiated and carried out.
 29. Theprocess as claimed in claim 28, characterized in that the reaction is anoxidation, preferably an oxidation by means of oxygen, in particularatmostpheric oxygen, as further reactant.
 30. The process as claimed inclaim 28, characterized in that the reaction is initiated and carriedout by means of a thermal treatment which is preferably carried out attemperatures in the range from 200° C. to 1250° C.